The Met Police said that PC Palmer's actions provided time for other officers to react and shoot and stop the assailant, who moments before had ploughed a vehicle into pedestrians on Westminster Bridge.

"PC Palmer did his duty. He stood his ground and placed himself between Parliament and a terrorist determined to harm those within.

"In doing so he made the ultimate sacrifice."

Days after his death, on March 27, his family paid tribute to him. They said: "We have been overwhelmed by the love and support of our family, and most especially, the outpouring of love and respect for Keith.

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"We want to thank everyone who has reached out to us over the past few days for their kindness and generosity.

"The police have been a constant, unwavering support at this very difficult time. It has made us realise what a caring, strong and supportive family Keith was part of during his career with the police. We can't thank them enough."

Floral tributes on Westminster Bridge following the terrorist attack in which four people were killed including PC Keith Palmer (Image: Kavita Hansla)

The statement added: “We would also like to express our gratitude to the people who were with Keith in his last moments and who were working that day. There was nothing more you could have done.